Electrical motive apparatus.



RJH. GAYLORD & G. B. CAPPS.

ELECTRICAL MOTIVE APPARATUS. APPLICATION FILED JULY 23.1914.

Patented July 31, 1917.

3 SHEETSSHEET 1.

R. H. GAYLORD & G. B. CAPPS.

ELECTRICAL MOTIVE APPARATUS.

APPLICATION HLED JULY 23. 191.4.

1,235, 1 32. Patented July 31, 1917.

3 SHEETSSHEET 2.

L/Z Cap v6,

R. H. GAYLORD & G. B. CAPPS. ELECTRICAL MOTIVE APPARATUS. APPLICATIONFILED JULY 23.1914.

1 ,235, 1 32. Patented July 31, 1917.

'3 SHEETS-SHEET 3.

2 b526 W I jfoer 2 W W UNITED STATES PATENT oFrIcE.

ROBERT H. GAYLORD, OF PASADENA, AND GUY B. CAPPS, 0F LOS ANGELES,CALIFORNIA.

ELECTRICAL MOTIVE APPARATUS;

Specification of Letters Patent.

Patented July 31, 191 "0.

Application filed July 23, 1914. Serial No. 852,531.

.Angeles and State of California, and GUY B. CArPs, residing at LosAngeles, in the county of Los Angeles and State of California, bothcitizens of the United States,- have invented a new and usefulElectrical Motive Apparatus, of which the following is a specification.

This invention relates to electrical motive apparatus for operation ofelevators, or hoists, or other apparatus presenting considerablemomentum when in operation, and the main object of the invention is toprovide for increasing theeffective speed of the motive means relativelyto the speed of the elevator or other apparatus, in starting andstopping the same, so as, on the one hand, to facilitate starting of themotive means under load, and, on the other hand, to enable the saidmotive means to run above the normal speed when the apparatus is beingbrought to rest, and to thereby enable the said motive means to deliverelectrical energy to the operating line or circuit at the same timeproducing an efiicient dynamic brake.

Our invention is especially advantageous in the operation of apparatussuch as above described by alternating current, an important object ofthe invention being to enable elevators and other apparatus to be drivenby alternating current, at higher speed than is practicable with theusual motive arrangements, while permitting of effective control instarting and stopping.

A further object of the invention is to provide, in an apparatus drivenby induction motors, means of control for variation of the speed,without undue complication. of the control apparatus, and. particularlywithout the use of shift gears.

Our invention, as hereinafter described, is particularly designed forthe operation of electric elevators by alternating current, in suchmanner as to provide for such operation under the conditions ofspeedgenerally obtained in practice. Electric elevators, particularlypassenger elevators, are in common practice, operated at a rate of speedas high as six hundred feet per minute, and for such high speeds thealternating current motor drive has not been found practicable, for thereasons hereinafter stated.

It has not been possible to obtain with an induction motor, the highstarting torque required with high speed elevators, without excessivecurrent flow in starting, which seriously affects the circuit and thesource of supply.

It has not been practicable to obtain efficiently with an inductionmotor, the variable speeds and gradual acceleration necessary for highspeed elevator operation, without making the control apparatus toocomplicated. An induction motor of the variable speed type is wastefulof energy at any speed other than its normal speed, and at any otherthan normal speed, will vary with the load, so that with the controllinglever in a given position, the motor will run slower under 'a heavy loadthan under a light load, making it diflicult for the operator toaccurately judge the speed of his car and thereby make an accurate stop.

Another and most serious dificulty in connection with the use of theinduction motor in high speed elevator" work is the incapability of suchmotors of producing dynamic braking action, by working either in aclosed braking circuit or in connection with the supply circuit. Forthis reason, elevators driven by an induction motor must depend whollyon a mechanical brake for deceleration and stopping. While themechanical brake is suitable for low speed elevators, where the speeddoes not exceed two hundred feet perminute, it is'not suitable for highspeed service, for-the reason that the brake must be adjusted .so thatit will bring a fully loaded car to a positive stop and when it is soadjusted, a lightly loaded carwill be stoppedtoo abruptly. Moreover,

the distance that the car will travel after throwing off the current andputting on the brake, will, with a mechanical brake, vary greatly withthe load and speed, since the braking resistance is constant and theenergy to be absorbed varies directly as the mass and as the square ofthe velocity of the car. Therefore the operator has to judge hisstopping distance according to the load and speed of the car, and oftenoverruns or ,falls short, bymisjudgment. The dynamic "brake, where itcan be used, largely overcomes this difliculty, as thebraking resistanceincreases with the velocity, so that the greater the momentum of the carthe greater will be the braking action, and the braking or stoppingdistance will vary relatively little under variations of load and speed,

the speed of the car may be varied while permitting the motor operatingthe same to be run at its normal and most efiicient speed.

By, providing for increase in the ratio of 'motor speed to car speed, instarting, we

are enabled to reduce the starting torque required, so that a lowstarting torque motor may be used, and the motor will start under loadwithout drawing an excessive current from the line, and at the same timegive a rapid and gradual acceleration to the car.

By providing for temporarily speeding up the motor relatively to the carspeed, in stopping or deceleration, the motor may be caused to runfaster than synchronous speed, and to deliver electrical energy to theline,

so as to exert a braking efi'ect on the car.

While our invention is applicable generally in connection withelectrical motor driven apparatus, we have for the purpose oof.illustration, shown it in the accompany.-

ing drawings as applied to operation of an elevator driven by inductionmotors.

Referring to the drawings: Figure 1 is a side elevation partly insection, showing one form of the invention.

Fig. 2 is a view similar to ing a modified form. I

-Fig. 3 is a cross section through the differential gearing, showinganother form of Fig. 1, showgearing.

Fig. 4 1s aview similar to Fig. -1, showinga form used for traction orhigh speed elevators. i 0

Fig. 5' is a side'elevation in detail of a brake.

Fig. 6 is a cross section through a modified form of differentialgearing.

Fig.7 is a diagrammatic view showing the connections. e

In the form shown in Fig. 1, 2 designates the shaft of the drivenapparatus, said shaft carrying, for example, drum l'for an elevatorcable, and said shaft carrying a gear 3, which is driven from a worm 4,the latter being mounted in suitable bearings 5. 6,

and -7 designate two alternating current induction motors, which arearranged'axially in line, motor 6 havinga shaft 8 which extends freelythrough the motor 7 with its end 9 journaled in the shaft 10 of the wormv 4. The motor 7 has a hollow shaft 11, through which the shaft 9.freely passes, and

carried rigidly on shaft 11 is a beveled gear;

, 12, while rigidly mounted on the shaft .9 is

a beveled gear 1'3, thegears 12 and 13 formmovement or to engage witswitch 9 having contacts g g lwire 35 with contact ing the two membersof a differential gear ing, beveled pinions 14 meshing between the gears12 and 13 and being carried by a casing 15, the latter being rigidlysecured to a '-flange 16 on the shaft 10. Brakes 17, 18

and 19 are respectivelyemployed for shaft 8 of motor 6, shaft 11 ofmotor 7, and the differential case 15, these brakes being similar inconstruction, and illustrated in detail in Fig. 5. 2O designates anelectromagnetic device formed in this instance by a solenoid witharmature 21 having a wedge 22, which is adapted to act between rollers23 on brake members 24 pivoted at 25 to a block 26, and

' having friction segments 27 adapted to bear against a friction drum28.- A rod 29 extends through both members 24, and com-' pressionsprings 30 act to force the members 24 toward each other and cause thefriction segments 27 to bear against the drum 28 and apply the brake.Release of the brake is effected by energization of the solenoid 20,which raises its armature 21, causing the wedge 22 to force apart themembers 24 and thus release the drum 28.

With this construction it is obvious that if motors 6 and 7revolve .atthe same speed and in the same direction as one another they'will rotategears 12 and 13 at the. same speed, thereby rotating the differentialgear case 15 at the same speed, and with it the worm 4 thus driving theshaft 2, drum 1 and car, not shown, at the maximum speed. If one of themotors is held stationary, the other motor will through its connectedgear 12 or 13 and pinions-14, drive the difi'erential gear case 15 at aslower speed, giving a corresponding slow speed of the drum and car.

' The control of the motors is indicated in the diagram in Fig. 7 andreferring thereto: 31 designates a controlling switch having lever 32adapted to be moved into engagement with contacts a, b, or c, to ve aforward the contacts, a, b or 0 for a reverse movement. of, e, f, g andit designate controlling switches, switch at. having contacts d d d d d01 and switch e having contacts e 6, e", e, 6

6, switch f, having contacts f F, f,

9 .9mm, switch 72. having contacts k 12. h, h, If, h 33, 34 and 35designate the three leads of the motor circuit; Wire 33 is connected bya wire 36 with contact d A wire 37 connects,

Wire 38' connects wire 34 with contact d wire 35 with contact d wire 33with contact e. wire 35 with contact e 3. wire 34 with contact e wire 34with contact f wire35 with contact 7. wire 33 with contact g. wire 34with contact 9 Wire 39 -connects Wire 40 connects Wire 41 connects Wire42 connects Wire 43 connects Wire 44 connects Wire 45 connects Wire 46connects Wire 47 connects wire 34 with contact 71.

provided for switch a solenoid 51 for switch 6, a solenoid 52 for switcha sole-' noid 53 for switch 9, and a solenold 54- for switch it. A wire55 connects contact a with one pole of solenoid 52. A wire 56 connectscontact 6 with one pole of solenoid 50. A wire 57 connects contact 0with one pole of solenoid 53. A wire 58 connects contact a with wire 55.Wire 59 connects contact b with one pole of solenoid 51. A wire. '60connects contact 0 with one pole of solenoid 54. A wire 61 connectscontacts 03 and a I A wire 62 connects contacts d and e. A wire 63connects contacts (2 and e. A wire 64 connects contacts 9 and h s A Iwire 65 connects contacts 9 and h A wire 66 connects contacts 9 and it.A wire 67 is connected with solenoid 50, and is connected by a wire 68with solenoid 51, and by a wire 69 with solenoid 52, and by a wire 70with solenoid 53, and by a wire 71 with solenoid 54. A wire 72 leadsfrom wire 69 to wire 4 A lead 73 from motor 6 connects with wire 62. Alead 74 from motor 6 connects with wire 61. Alead 75 from motor 6connects with wire 63. A wire 76 connects lead 74 with one poleof'solenoid of brake 17, and a wire 77 connects lead 75 with the otherpole of solenoid of brake 17. A wire 78 connects I 4 contact f with onepole of solenoid of differential gear brake 19, and a wire 7 9 conthatbrake. The controlling lever 32 is next nects contact y with the otherpole of the solenoid of differential gear brake 19. One lead 80 frommotor 7 connects with wire 65. Another lead 81 from motor 7 connectswith wire 64. Another lead 82 from motor 7 connects with wire 66. A wire83 connects lead 81 with one pole of the solenoid of switch 18, and awire 84 connects the lead- 82 with the other pole ofthe solenoid ofswitch 18. Wire 85 connects lever 32 with wire 33. D, E, F, G, Hdesignate the respective armatures for the respective solenoids 03, e,f, g and h.

The operation is as follows: For starting at slow speed, lever 32 ismoved onto contact a, hereby closing a circuit as follows:

from line wire 33 through lever switch 32 to contact a, through wire 55,through solenoid 52 and wire 86 to wire 72 and wire 35, energizingsolenoid 52, and lifting its armature F, which tacts f f and betweencontacts f f thereby establishing the following circuit: from wire 35through wire 43 to contact 7 to contact f to wire 78, solenoid of brake19,

through wire 79 to contact f to contact f to wire 34. Solenoid ofdifferential gear brake 19 is thus energized, which releases moved tocontact 5, which establishes a circloses circuit between con- D, closingcontact d and (Z 03 and d (5 and d whereupon the circuits areestablished as follows: from wire 35 through wire 38 to contact d to.contact 03 wire 62 ,wire 73 to motor 6,.also from wire 34 to contact dto contact d through wire 61 to wire 74 and motor 6, and also from wire33 through wire 36 to contact d to contact 01 and through wire 63 tolead 75 and motor 6, and also establishes a circuit from wire 74 throughwire 76 to solenoid of brake 17 and from this solenoid through wire 77to wire 75, thereby releasing brake 17 of motor 6, and also closing thecircuit through motor 6, whereupon as motor 7 is still stationaryandunder its brake 18, motor 6 operates through its shaft 8 to drivegear 13, and through the pinions 14 operates the differential gearcasing 15 around the stationary gear 12, the latter being heldstationary with shaft 11 of motor 7, and thereby driving thedifferential gear casing 15 and shaft 10 attached thereto together withworm 4, gear 3 and drum 1 at a reduced speed.

After this starting, to obtain full speed, the lever 32 is moved tact 0,thereby establishing circuits as follows: from contact 0 through wire 57through'solenoid 53 through wire 70 to wire 71 to wire 35, therebyenergizing solenoid switch 9 and attracting its armature G therebyclosin contacts g g g 9 g and 9 which esta lishes the from wire 35through wire 46 to contact 9 to contact 9 through wire 65 to wire 80 andmotor 7, and from wire 34 through wire 45 to contact 9 to contact 9through wire 64 to wire 81 and motor 7, and from wire 33 through wire 44to contact 9 to contact 9 through wire 66 to wire 82 and motor 7 andfollowing clrcuits still farther onto conalso from wire 81 through wire83 and solei is running, it operates through its shaft 11 j and gear-12'to coact with gear 13 driven from motor 6 to drive the differential gearcasing 15 at the same speed as the motor shaft, thereby driving worm 4,gear 3 and drum 1 at maximum speed.

When it is desired to slow down, the'lever l 32 is movedofi' fromcontact 0, thereby cutting off the current through the before describedconnections from motor 7, and deenergizing the solenoid of brake 18 andperi mitting brake 18 to hold shaft of motor 7 stationary, therebytending to reduce the speed of the difierential housing and the 'carconnected thereto. ,The momentum of the drum and car tends tomaintain'the motor 6 through the befored'escribed connections anddeenergizes solenoid "of'brake 17 causing the latter to set, and thenthe lever 32 is moved off from contact a, which deenergizes the solenoidof brake 19, which causes the latter to set tight on the diiferentialgear casing 15, and thus act as a further brake, although it will beapparent that the brake on the dilferential gear casing 15 is not anessential feature, but is an added safeguard.

In running in the opposite direction, the

lever 32 is first moved onto. contact a through wire 58 to wire throughsolenoid 52 wire 86 and wire 72 to wire 35, thereby energizing solenoid52 and raising its armature F and closing contacts 7, f f f whereupona,circuit is established as follows: from Wire 35 through wire 43 tocontact f to contact and wire 78 to solenoid of differential gear brake19 through wire 7 9 to contact to contact f to wire 34, thus releasingbrake 19 of the differential-gear. The lever 32 is next moved ontocontact 5 whereupon circuits are established as fol lows: from contact 5through wire 59 to solenoid 51 through wire 68 to wire 69 and wire 35,thereby energizing solenoid 51 and attracting armature E, therebyestablishing a circuit through motor 6 and solenoid of brake 17, therebyreleasing brake 17 the circuits through motor 6 being as follows:

' from wire 33 through wire 39 to contact 6 to contact 6 to wire 63 towire 75 and motor 6 from wire 34 through wire 41 to contact" e tocontact 6 and wire 62 to wire 7 3' and motor 6; and from wire 35throughwire 40 to contact a to contact e to wire 61 to, wire 74 and motor 6,these circuitsgiving a reverse rotation of the motor6, by reason of thewires 41 and 46 of solenoid switch e being connected respectively towires 34 and 35, while .in forward running, the concircuits areestablished as follows: from contact 0 through wire 60 to solenoid 54and wire 71 to wire 69 wire 72 and wire 35, thereby energizingsolenoid54 and attracting armature'H;,whereupon circuits are established asfollows: from wire 33 through wire 47 to contact h to contact 72, towire 66 to wire 82 to motor 7; also from wire 34 through wire 49 tocontact 71? to contact 71. wire 87 to wire 80 and motor 7, and also fromwire 35 through wire 48 to contact 71. to contact h to wire 86 and wire81 and motor 7. Circuit is also established from wire 81 through wire 83solenoid of brake 18 and wire 84 to wire 82. This energizes the solenoidof brake 18 and releases brake 18 and supplies current to motor 7, whichnow operates in unison with motor 6 and drives the worm 4, gear 3, anddrum 1 at full speed. When'thus moving reversely to come to a reducedspeed, the lever 32 is moved off from contact 0 thereby through thebefore described connections stopping motor 7 and setting brake 18. Themomentum of the drum and car will have a tendency to revolve the worm 4'ahead of the normal speed of motor 6, which will be retarded by motor 6,which will act as a brake. In coming to a stop, the lever 32 is movedoff from contact 5 which stops motor 6 and sets brake 17 and by movinglever 32 011' from contact a the solenoid, of the differential gearbrake is deenergized, setting that brake also.

When running in either direction at full speed, upon slowing down toreduce speed by moving lever 32 off from contacts a or 0 the motor'which continues; in operation speeds up inexcess of synchron ism, dueto the car momentum driving same and acts as a dynamic brake, causingthe motor to act as a generator, and the current 'thusproducedjsreturned to the line. Thus, the energy which is employed to bring thecar to a stop is in part turned back into'the line, whereas in othersystems where a direct I current motor is employed and the dynamicbrakin efiect made use of, resistance is utilize and the energy iswholly dissipated. When the motor, acting as a generator, graduallyovercomes the car momentum and the motor has slowed down to .synchronismwith the alternating supply circuit, its

'dynamic braking action ceases, and the nections are through solenoidswitch (2, in generator automatically becomes a motor which Wires 38and'37 are respectively con- 1 nected to wires 35 and 34.

The motor 6 thus operates through the beforedescribed gearing to revolvethe drum 1 in the opposite direction atjythe reduced speed, as at thistime the motor 7 is sta- "tionary and its brake 18 holds shaft 11- andgear 12 stationary.

To run reversely at full speed the lever 32 is next moved onto contact 0whereupon and maintains the reduced speed. The

motor is then brought to rest by moving speed. By suitably proportioningthe gears tion of its full speed before the dynamic braking effect isexhausted. Thus, as shown in Fig. 3, the gear 12*, may be smaller thanthe gear 13, so as to increase the.

speed reduction of the car relatively to the motor, in starting or atslow speed, and to increase the speeding up of the motor in stopping, soas to extend the dynamic braking action. I

By the above described means the car may be run at either low or highspeed without the use of shift gears and with the induction motive meansrunning at normal speed. As such means also provides for reducing thestarting torque on thestarting motor, it enables a motor with lowstarting torque to be used and also eliminates the overdraft on thesupply circuit and source of current by rush of current to the inductionmotor, in starting under excessive load.

Fig. 2 shows a modified form in which the motors 6 and 7 are on oppositesides of the worm 4". In this form it is necessary to carry the shaft 9of motor 6 completely through the worm 4: to connect withthedifferential gear. In this form, the operation is precisely the sameexcept for the relative arrangement of the motors and their brakes.

. The form shown in Fig. 4is adapted for traction elevators in which 1designates the drum, which constitutes the casing of the differentialgear consisting of gears 12" and 13, which are respectively carried onshafts 8 and 11 of motors 6 and '2' respectively, pinions 149 beingmounted directly on the drum; The brake 28 of solenoid 19 is directlymounted on the drum 1*, and the brake 28 of motor 7 is operated bysolenoid 18 while brake 28 of motor 6" is operated by solenoid 17 r Fig.6 shows differential gearing adapted to be used in the traction type ofFig. 4, to give a different gear reduction in which the gear 12 issmaller than the gear 13 and pinions 14 are set at a correspondingangle.

What we claim is:

l. A driven element, two induction motors, braking means for the motorsrespectively, and means connecting said motors to the driven elementwhereby when the motors are operated at synchronous speed in the samedirection as one.another the driving element is driven and when onemotor is held against rotating the other motor will be operated by thedriven element at a greater speed than synchronous s eed so that saidoperating motor will pro uce dynamic braking action.

2. The method of electric drive, which method comprises operatinginduction motors in the same direction as one another at normal speed todrive a driven element, and then reducing the speed of one motor tocause the driven element to drive the other motor at a higher rate ofspeed than said normal speed so as to produce dynamic braking action ofsaid other motor.

3. A driven element, two motors, gearing between the two motors fordriving the driven element, a brake for each motor, solenoids forcontrolling said brakes, controlling means, a supply circuit, meansoperated by said controlling means in one position for connecting onemotor and the associated brake solenoid with the supply cir cuit, andwhen in another position to also connect the other motor and its brakesolenoid to the supply circuit.

4. The combination of two electric induction motors, electric supplyconnections therefor, bevel gears connected respectively with saidmotors, an intermediate member carrying bevel gears engaging theaforesaid bevel gears to form a differential gearing adapted to permitturning of the motois in the same direction as one another, a loaddevice connected to be driven by and to drive said intermediate member,and means for arresting one of said motors to cause the other motor torun at an increased speed by operation of said load device.

5. A driven element, two motors, a hollow shaft 011 one motor, a shafton the other motor extending through the hollow shaft, a gear on eachshaft, pinions between said gears, a casing carrying said pinions anddriving the drlven element, a brake for the hollow shaft, and a brakefor the other shaft.

6. A driven element, two motors, a hollow shaft on one motor, a shaft onthe other motor extending through the hollow shaft, a gear on eachshaft, pinions between said gears, a casing carrying said pinions anddriving the driven element, a brake for the hollow shaft, a brake forthe other shaft, and a brake for the casing.

7. A driven element, two motors, a hollow shaft on one motor, a shaft onthe other motor extending through the hollow shaft, a gear on eachshaft, pinions between said gears, a casing carrying said pinions anddriving the driven element, a brake for the hollow shaft, a brake forthe other shaft, and a solenoid for releasing such brake, each solenoidbeing in circuit with the associated motor.

' 8. In elevator operating mechanism, two electric induction motors,electric supply connections therefor, a differential gearing comprisingtwo ear members connected respectively to sai motors and an intermediatemember provided with gears engaging the aforesaid gear'members to permitof turning of the motors in the same direction as one another, saidintermediate member i being connected to the elevator car to drive thesame and to be driven thereby, and

means for arresting one of said motors tocause the other motor to bedriven at an increased speed so as to act as a dynamic brake. V

9. In combination a differential gear comprising two opposite gearmembers, an intermediate member provided with gears rotatablymountedthereon and engaging the aforesaid gear members, two electric inductionmotors adapted to turnin the same direction as one another and connectedrespectivelyto said opposite gear members to drive said opposite gearmembers and theintermediate member at the same rotative speed, and meansfor arresting one of said normal speed so as to produce connected tosaid motors motors to enable the intermediate member to drive the othermotor at an increased speed, so that said other motor w1ll act as adynamic brake.

current supply circuit,'tw'o induction motors connected thereto, adriven element, a differential gearing having opposite members an havingan intermediate member connected to said driven element to allow turningof the motors in the same direction as one another, and means forarresting one of'said motors to causethe other motor to operate at ahigh speed relatively to the driven member.

11.-In combination with an alternating current supply circuit, aninduction motor connected thereto, a driven element, means connectingsaid driven element to said motor to drive said driven element at adefinite speed when the motor is running at normal speed, and means forchanging the connection between the motor and driven element to causethe motor to run above normal'and above synchronous speed, while thedriven element isrunning at or below normal speed,

whereby the motor is caused to act as agenerator, and as a dynamicbrake.

12. The method of electric drive, which method com rises operatingdifierentially connected in uction motors at normal speed to move aload, and then mechanically arresting one motor to cause the load todrive the other motor at a higher speed than said dynamic braking actionof said other motor.

13. The method of electric drive, which method comprises energizingdifferentially connected motors to cause operation thereof atsynchronous speed in the same direction as one another to move a load,and then producing braking action on one of said motors anddeenergization thereof so-that' the inertia of the moving load will runthe other motor above. synchronous s eed.

14. In combination, two induction motors, a differential connection forsaid motors, a

10. In combination with an alternating .ber to rest.

rotative member connected to and driven by the differential when themotors are running at synchronous speed in the same d rection asioneanother and driving the differential when one of the motors is cut out,

there being means to reduce the speed of said motor, so that the speedof the other tarding the same, braking means for each motor shaft, andgearing connecting each motor shaft with the driven member to cause thedriven member to operate at the same speed as the motor shafts when bothmotors are operating and to cause the-driven member to operate at areduced speed relative to one of the motors when the othermotor isretarded by its brake, whereby the load device may be operated at areduced speed in starting and may operate one of the motors at anincreased speed in stopping toproduce a dynamic braking action of saidmotor.

16. The combination of a driven member,

two motors, each provided with driving con- -nections .and with a shaft,braking means for each shaft, differential gearing connecting both ofsaid shafts 'to said driven member to operate" the driven member by thejoint action of said motorsand to cause the driven member to operate oneof the motors at an increased speed when the other motor is retarded byits braking means.

17. A driven element, differential gearing connected to drive the same,two motors connectedto opposite members of said differential gearing forjoint operation of said driven element, braking means for one of saidmotors to cause the driven member to operate at a reduced speedrelative" to the other motor so as to reduce the speed of the drivenmember in starting and to increase the speed of said other motor forproducing a dynamic braking action of said other motor in stopping, andbraking means for sald other motor to bring the driven mem- 18.. A loaddeviceya diflerential gear conload device and to be operatedthereby,'two motors provided with operating connections and havingshafts connected to opposite members of said. differential gear tooperate the load device by the joint action of said necteil to said loaddevice to operate said motors, means for braking one of said motors tocause the load to. operate at a reduced I speed relative to the othermotor, whereby the load device may be operated at a reduced speed instarting and may operate the said other motor at an increased speed instopping to produce a dynamic brake action, and means for braking saidother motor to bring the load device to rest.

19. In combination, induction motors, a driven element difierentiallyconnected to the induction motors, brakes for the induction motors, andmeans to establish an electric circuit for release of one brakeandenergization of its associated motor and to then establish anelectric circuit for release of the other brake and energization of itsassociated motor to drive said last named motor in the same directionand at the same speed as the first named motor.

20. In combination, induction motors, a driven element diflerentiallyconnected to the induction motors, brakes for the induction motors, andmeans to establish electric circuits for release of the brakes andenergization of their associated motors and to then break one of saidcircuits to deenergize one of said motors and to set the associatedbrake to allow the driven element to drive the other motor at a higherspeed than synchronous speed so as to produce dynamic braking action ofsaid other motor.

21. The method of electric drive, which method comprises operatinginduction motors at normal speed to drive a driven element, and thenbringing one motor to a stop to cause the driven element to drive theother motor at a higher rate of speed than said normal speed so as toproduce dynamic braking action of said other motor.

22. The combination of two induction motors, electric supply connectionstherefor, bevel gears connected respectively with said motors, anintermediate member carrying bevel gears engaging the aforesaid bevegears to form a differential gearing, a load device connected to bedriven by and to drive said intermediate member, and means for stoppingone of said motors to cause the other motor to run at an increased speedby operation of said load device.

23. In elevator operating mechanism two induction motors, electricsupply connections therefor, a diflerential gearing comprising two gearmembers connected respectively to said motors, and an intermediatemember provided with gears engaging the aforesaid gear members, saidintermediate member being connected to the elevator car to drive thesame and to be driven thereby, and means for stopping one of said motorsto cause the other motor to be driven at an increased speed so as to actas a dynamic brake. 1

24:- In combination, a differential gear comprising two opposite gearmembers and an intermediate member provided with gears rotativelymounted thereon and engaging the aforesaid gear members, two inductionmotors connected respectively to said opposite gear members to drivesaid opposite gear members and the intermediate member at the samerotative speed, and means for stopping one of said motors to enable theintermediate member to drive the other motor at an increased speed sothat said other motor will act as a dynamic brake.

25.- In combination with an alternating current supply circuit, twoinduction motors connected thereto, a driven element, a differentialgearing having opposite members connected to said motors and having anintermediate member connected to said driven element, and means forstopping oneof said motors to cause the other motor to operate at higherspeed relative to the driven member.

In testimony whereof, we have hereunto set our hands at Los Angeles,California,

this 16th day ofJuly, 191

ROBERT H. GAYLORD. GUY B. CAPPS.

